Abstract:
Wetlands are vital ecosystems that provide essential ecological services.
Bellanwila-Attidiya Wetland, which is one of the most significant urban wetlands in Sri Lanka, has experienced considerable land use and land cover (LULC) changes in the past few decades, causing serious environmental impacts. The objectives of this research were to assess the land use and land cover changes within the Bellanwila-Attidiya wetland area between 1995-2024 and to evaluate the resulting environmental impacts. Supervised classification of Landsat images from 1995, 2011, and 2024 was performed using ArcGIS, followed by a change detection analysis to track LULC changes. The results of LULC changes revealed a sharp decline in vegetation cover from 60% in 1995 to 36% in 2011, reflecting intense urbanization, with only a slight recovery to 38% by 2024. Built-up areas have increased significantly from 119.92 ha (32%) in 1995 to 198.97 ha (54%) in 2024, becoming the dominant land cover. To assess environmental impacts of LULC changes in the Bellanwila-Attidiya Wetland, a household survey was conducted alongside the geospatial analysis with 55 long-term residents selected through stratified random sampling from three Grama Niladhari divisions near the wetland. Moreover, the analysis of environmental impacts was further supplemented by key informant interviews to gather additional insights. The results of the environmental impacts indicated that during 1995-2024, about 110 ha of wetland habitat were lost according to the spatial analysis of the study area.
Invasive alien species such as Annona glabra, Eichhornia crassipes, and Hypostomus plecostomus have spread rapidly due to increase of built-up areas.
Between 1995 and 2024, vegetation cover in the Bellanwila-Attidiya Wetland decreased by 37.8%, with 39.2% of the loss converted to built-up areas, 7% to water bodies, and 0.9% to open areas, indicating a significant loss in vegetation cover. A significant reduction in biodiversity has been observed, with a 52% reduction in bird species, 87% reduction in fish species and extinction of amphibian species such as Philautus leucorhinus. These findings emphasize the urgent need for integrated conservation and land-use planning to protect the Bellanwila-Attidiya Wetland and ensure the survival of its biodiversity.
